A quarrel broke out between them,_____Mary threw a mirror on the ground and broke it into pieces
问题描述：
A quarrel broke out between them,_____Mary threw a mirror on the ground and broke it into pieces
A with whom B which C during which D about which
可是为什么不选B
答
"which" 代表上半句的" quarrel ",也就是说Mary 做的那些事情都是相对于"quarrel"做出的,所以应该是在quarrel期间,也就是：during which.
或者你也可以从后半句里发现那是一个完整的句子,所以缺少的是介词和定语.